Acute Management Overview

Agent Identification

Hydrogen cyanide has a distinctive bitter almond odor, but some individuals cannot detect it and consequently, it may not provide adequate warning of hazardous concentrations. The odor of hydrogen cyanide is detectable at 2-10 ppm (OSHA PEL = 10 ppm), but does not provide adequate warning of hazardous concentrations. Perception of the odor is a genetic trait (20 % to 40 % of the general population cannot detect hydrogen cyanide).

Hydrogen cyanide is highly toxic by all routes of exposure. The amount of cyanide, the duration of exposure, and the route of exposure all influence the time to onset and the severity of illness.

With higher doses the time of onset of symptoms typically is seconds following inhalation of gaseous hydrogen cyanide and may cause abrupt onset of profound CNS, cardiovascular, and respiratory effects, leading to death within minutes. Signs and symptoms may present over a much longer period of time if the the poisoning is gradual with lower doses.

Liquid agent, which is readily absorbed through skin (especially in young children and pregnant women), can produce symptoms immediately or be delayed up to an hour.

Responders should obtain assistance in identifying the chemical(s) from container shapes, placards, labels, shipping papers, and analytical tests. General information on these identification technicques is located in Emergency Response Guidebook.

Cyanide Agent Specific Triage

High concentrations of cyanide gas can cause death in minutes; however, low concentrations may produce symptoms gradually, causing challenges for the triage officer. Generally, a person exposed to a lethal amount of cyanide will die within 5 to 10 minutes of exposure.

Casualties exposed to cyanide vapor who have survived for 15 minutes can be categorized as minimal or delayed.

Contamination of conventional injuries with cyanide can result in respiratory depression and reduction of the oxygen carrying capacity of the blood. Urgent use of cyanide poisoning antidote is required. Oxygen therapy combined with positive pressure resuscitation may be required sooner in the presence of marked hemorrhage from the conventional injury. Opiates and other drugs that reduce respiratory drive must be used with extreme caution.

Decontamination

Patients exposed only to hydrogen cyanide gas who have no eye irritation do not need decontamination. They may be transferred immediately to the Support Zone. Other patients will require decontamination.

Clinical Signs and Symptoms

Cardiovascular effects - Initially bradycardia and hypertension may occur, followed by hypotension and tachycardia. The terminal event is consistently bradycardia and hypotension.

Respiratory - Initial patient findings may include increased respiratory rate, shortness of breath, and chest tightness. With progression of poisoning, respirations become slow and gasping. Central cyanosis may or may not occur. Pulmonary edema may occur.

GI toxicity following ingestion of cyanide may occur. This may include abdominal pain, nausea and vomiting.

Skin - A cherry red skin color may be present as the result of increased venous hemoglobin oxygen saturation. Cyanide does not directly cause cyanosis. If present, it is secondary to shock.

Ocular - Direct contact to liquid cyanide can result in eye irritation and swelling.

Children and pregnant women are much more vulnerable than adults to cyanide agent toxicity.

Differential Diagnosis

In mass casualty events cyanide or nerve agents can both present with sudden loss of consciousness followed by convulsions and apnea. Nerve agents typically have miosis, copious oral and nasal secretions, and muscle fasiciculations. Cyanide has normal or dilated pupils, few secretions and muscular twitching.

Cherry red skin color if present is suggestive of cyanide toxicity

One would have to have a high index of suspicion to focus on cyanide as the etiology of an individual presenting with loss of consciousness followed by convulsions and apnea, as this chain of events is common as the result of multiple etiologies. However in a mass casualty event only three agents that can be dispersed via aerosol or gas can cause a group of people to simultaneously fall, lose consiousness and seize: nerve agent cyanide, and possibly hydrogen sulfide.

Hot Zone

Rescuers should be trained and appropriately attired before entering the Hot Zone. If the proper equipment is not available, or if rescuers have not been trained in its use, call for assistance in accordance with local Emergency Operational Guides (EOG). Sources of such assistance should be obtained from a local HAZMAT teams, mutual aid partners, the closest metropolitan strike system (MMRS) and the U. S. Soldier and Biological Chemical Command (SBCCOM)-Edgewood Research Development and Engineering Center. SBCCOM may be contacted (from 7:00 AM - 4:30 PM EST call 410-671-4411 and from 4:30PM - 7:00AM EST call 410-278-5201), ask for the Staff Duty Officer.

Hot Zone

Agent Identification

Hydrogen cyanide has a distinctive bitter almond odor, but some individuals cannot detect it and consequently, it may not provide adequate warning of hazardous concentrations. The odor of hydrogen cyanide is detectable at 2-10 ppm (OSHA PEL = 10 ppm), but does not provide adequate warning of hazardous concentrations. Perception of the odor is a genetic trait (20 % to 40 % of the general population cannot detect hydrogen cyanide).

Hydrogen cyanide is highly toxic by all routes of exposure. The amount of cyanide, the duration of exposure, and the route of exposure all influence the time to onset and the severity of illness.

The time of onset of symptoms typically is seconds following inhalation of gaseous hydrogen cyanide and may cause abrupt onset of profound CNS, cardiovascular, and respiratory effects, leading to death within minutes.

Liquid agent, which is readily absorbed through skin (especially in young children and pregnant women), can produce symptoms immediately or be delayed up to an hour.

Responders should obtain assistance in identifying the chemical(s) from container shapes, placards, labels, shipping papers, and analytical tests. General information on these identification technicques is located in Emergency Response Guidebook.

Persons whose clothing or skin is contaminated with cyanide-containing solutions can secondarily contaminate response personnel by direct contact or through off-gassing vapor.

Rescuer Protection

Hydrogen cyanide is a highly toxic systemic poison that is absorbed well by inhalation and through the skin. Victims exposed only to hydrogen cyanide gas do not pose secondary contamination risks to rescuers, but do not attempt resuscitation without a barrier. Victims whose clothing or skin is contaminated with hydrogen cyanide liquid or solution can secondarily contaminate response personnel by direct contact or through off-gassing vapor. Avoid dermal contact with cyanide-contaminated victims or with gastric contents of victims who may have ingested cyanide-containing materials.

Skin Protection: Chemical-protective clothing is recommended because both hydrogen cyanide vapor and liquid can be absorbed through the skin to produce systemic toxicity.

Level A - protective clothing is the highest level of protection. Level A includes a Self Contained Breathing Apparatus (SCBA) with a fully encapsulating vapor tight suit with gloves and booties attached to the suit (tanks last from 1/2 hour to 1 hour).

Level B - requires the use of SCBA but has lesser skin protection. Level Bs are chemical resistant suits that are designed for splashes of liquids but not for gas or vapor hazards. A young soldier can last about 2 hours on a hot day with an external air hose.

Level C is similar to B with the exception of the type of respiratory protection. The SCBA is replaced with an Air Purifying Respirator.

Level D protective clothing is utilized when there are no respiratory hazard and no major skin hazard considerations. Level D for hospital personnel includes scrubs, safety glasses, shoe covers, and possibly a face shield.

Triage

Chemical casualty triage is based on walking feasibility, respiratory status, age, and additional conventional injuries. The triage officer must know the natural course of a given injury, the medical resources immediately available, the current and likely casualty flow, and the medical evacuation capabilities. General principles of triage for chemical exposures (cyanide specific triage foci) are presented in the management section.

General Principles of Triage for Chemical Exposures

Severe casualty triaged as immediate if assisted breathing is required.

Blast injuries or other trauma, where there is question whether there is a chemical exposure, victims must be tagged as immediate in most cases. Blast victim's evidence delayed effects such as ARDS, etc.

Mild/moderate casualty: self/buddy aid, triaged as delayed or minimal and release is based on strict follow up and instructions.

If there are chemical exposure situations which may cause delayed but serious signs and symptoms, then over-triage is considered appropriate to the proper facilities that can observe and manage any delayed onset symptoms.

Expectant categories in multi-casualty events are those victims who have experienced a cardiac arrest, respiratory arrest, or continued seizures immediately. Resources should not be expended on these casualties if there are large numbers of casualties requiring care and transport with minimal or scant resources available.

In a given category prioritize a child, pregnant woman over a non-pregnant adult.

Cyanide Agent Specific Triage

High concentrations of cyanide gas can cause death in minutes; however, low concentrations may produce symptoms gradually, causing challenges for the triage officer. Generally, a person exposed to a lethal amount of cyanide will die within 5 to 10 minutes of exposure.

Casualties exposed to cyanide vapor who have survived for 15 minutes can be categorized as minimal or delayed.

Contamination of conventional injuries with cyanide can result in respiratory depression and reduction of the oxygen carrying capacity of the blood. Urgent use of cyanide poisoning antidote is required. Oxygen therapy combined with positive pressure resuscitation may be required sooner in the presence of marked hemorrhage from the conventional injury. Opiates and other drugs that reduce respiratory drive must be used with extreme caution.

Clinical Signs and Symptoms

Hydrogen cyanide acts as a cellular asphyxiant. By binding to mitochondrial cytochrome oxidase, it prevents the utilization of oxygen in cellular metabolism. The CNS and myocardium are particularly sensitive to the toxic effects of cyanide.

Children exposed to the same level of cyanide agents as adults will usually receive higher doses because they have greater lung surface area: body weight ratios and increased minute volume: weight ratios.

CNS - Initial signs and symptoms especially with lower dose exposures are nonspecific and include excitement, dizziness, nausea and vomiting, headache and weakness. Progression of symptoms (pending exposure levels) can include increased lethargy, tetany, convulsions, and loss of consciousness. Young children, especially under the age of four, are more prone to develop seizure disorders secondary to hypoxia, or other CNS insult.

Cardiovascular - Arrhythmias can occur in cases of severe poisoning. Bradycardia, hypotension followed by death can occur. Transient hypertension and tachycardia may be early findings.

Respiratory - Initial patient findings may include shortness of breath, chest tightness, and increased respiratory rate. With progression of poisoning, respirations become slow and gasping. Central cyanosis may or may not occur. Pulmonary edema may occur.

Dermal - Systemic absorption can occur. High ambient temperate, relative humidity results in increased absorption. Children are more vulnerable to these toxicants being absorbed through the skin because their skin is thinner, contains more moisture, and they have a larger surface area to weight ratio than adults. Pregnant women also will have increased absorption through the skin because of the increased vascularity and vasodilatation associated with pregnancy.

Ocular - Direct contact to liquid cyanide can result in eye irritation and swelling.

Differential Diagnosis

In mass casualty events, cyanide or nerve agents can both present with sudden loss of consciousness followed by convulsions and apnea. Nerve agents typically have miosis, copious oral and nasal secretions, and muscle fasiciculations. Cyanide has normal or dilated pupils, few secretions and muscular twitching.

Cherry red skin color if present is suggestive of cyanide toxicity

One would have to have a high index of suspicion to focus on cyanide as the etiology of an individual presenting with loss of consciousness followed by convulsions and apnea, as this chain of events is common as the result of multiple etiologies.

Pediatric/Obstetric/Geriatric Vulnerabilities

Children exposed to the same level of cyanide agents as adults will usually receive higher doses because they have greater lung surface area: body weight ratios and increased minute volume: weight ratios.

Young children especially under the age of four are more prone to develop seizure disorders secondary to hypoxia, or other CNS insult.

Children are more vulnerable to these toxicants being absorbed through the skin because their skin is thinner, contains more moisture, and they have a larger surface area to weight ratio than adults.

In animal studies, it has been documented that sodium thiosulfate does not cross the placenta when utilized to treat cyanide toxicit,y but by treating the mother the cyanide levels in the fetus were lowered.

Antidote Dosing and Sequencing:

When possible, treatment with cyanide antidotes should be given under medical supervision to unconscious victims who have known or strongly suspected cyanide poisoning. Amyl nitrite has the advantage of being able to be given quickly without IV access. AMYL and SODIUM NITRITE have the potential to put the fetus of a pregnant woman at serious risk. In addition, there is increased vulnerability of infants and young children, those with active respiratory disease or diminished pulmonary reserve as well as those who have cardiovascular disease, particularly the elderly or frail, to increased methemoglobin levels (especially if combined with carbon monoxide exposure). If you are concerned that a patient is not oxygenating well such as in smoke exposure consider going directly to hydroxocobalamin or sodium thiosulfate.

Therefore, initial treatment with hydroxocobalamin is recommended vs. amyl and sodium nitrite in pregnant women, infants, young children (especially with co-morbidities such as smoke inhalation). An IO needle can be placed in the hot zone while wearing level A PPEs to facilitate treatment.

Amyl nitrite perle should be broken onto a gauze pad and held under the nose, placed under the lip of a facemask, or over the Ambu-valve intake. The patient should inhale for 30 seconds of each minute and a new perle should be utilized every three minutes if sodium nitrite infusions will be delayed. CAUTION AMYL NITRITE MAY CAUSE SIGNIFICANT HYPOTENSION AND IF TAKEN WITH DRUGS LIKE VIAGRA, CIALIS, OR LEVITRA (OTHER NITRITE-CONTAINING DRUGS), THIS EFFECT IS MAGNIFIED, POTENTIALLY CAUSING FAINTING AND EVEN DEATH.

As soon as IV access has been achieved in a symptomatic patient DC the perles and initiate IV sodium nitrite (ASAP).

The usual adult dose is 10 ml of a 3 % solution (300 mg).

The pediatric dose is 0.12 to 0.33 ml/kg.

It should be infused over no less than 5 minutes (monitor BP frequently).

In patients who initially improve with nitrite therapy, but then exhibit signs or symptoms of hypoxia/cyanosis, a diagnosis of methemoglobinemia should be considered in the differential diagnosis along with continued cyanide toxicity. See methylene blue treatment in Hospital Management.

Repeat one-half of the initial dose in 30 minutes if there is an inadequate clinical response or at 2 hours for prophylaxis.

Hydroxocobalamin

A dose of 70 mg/kg (not to exceed 5 grams initially) administered over 15 minutes is recommended. This dose can be given IV push in situations of cyanide induced cardiac arrest. (Adult† Pediatric‡ Pregnancy§)

Depending upon the severity of the poisoning and the clinical response, a second dose of 70 mg/kg (not to exceed 5 g) may be administered by intravenous infusion for a total dose of 10 g. The rate of infusion for the second dose may range from 15 minutes (for patients in extremis) to two hours, as clinically indicated

Many patients with cyanide poisoning will be hypotensive; however, elevations in blood pressure have also been observed in known or suspected cyanide poisoning victims. Elevations in blood pressure (≥180 mmHg systolic or ≥110 mmHg diastolic) were observed in approximately 18% of healthy subjects (not exposed to cyanide) receiving hydroxocobalamin 5 g and 28% of subjects receiving 10 g. Increases in blood pressure were noted shortly after the infusions were started; the maximal increase in blood pressure was observed toward the end of the infusion. These elevations were generally transient and returned to baseline levels within 4 hours of dosing.

While a safe drug, animal and anecdotal human studies have demonstrated limited or no additional therapeutic benefit by administering sodium thiosulfate in addition to treatment with hydroxocobalamin.

Physical incompatibility (particle formation) and chemical incompatibility were observed with the mixture of hydroxocobalamin in solution with selected drugs that are frequently used in resuscitation efforts. Hydroxocobalamin is chemically incompatible with sodium thiosulfate or sodium nitrite. Therefore, these and other drugs should not be administered simultaneously through the same intravenous line as hydroxocobalamin. If a second line is unavailable thoroughly flush the single line prior to administering sodium thiosulfate or sodium nitrite.

Ingestion Exposure

Do not induce emesis. If the victim is symptomatic, immediately institute emergency life support measures including the use of a cyanide antidote kit. If the victim is alert, asymptomatic, has a gag reflex, and it has not been done previously, give activated charcoal as soon as possible. Because cyanide absorption from the gut is rapid, the usefulness of activated charcoal will depend on how quickly after ingestion it can be administered.

Administer slurry of activated charcoal at 1 gm/kg (usual adult dose 60-90 g, child dose 25-50 g). A soda can and a straw may be of assistance when offering charcoal to a child.

Toxic vomitus or gastric washings should be isolated (e.g., by attaching the lavage tube to isolated wall suction or another closed container).

Because of potential toxicity of vomitus/aspiration, recommend consultation with Emergency Physician prior to administration of charcoal (if possible).

Victim Removal

If victims can walk, lead them out of the Hot Zone to the Decontamination Zone. Victims who are unable to walk may be removed on backboards or gurneys; if these are not available, carefully carry or drag victims to safety. Should there be a large number of casualties, and if decontamination resources permit, separate decontamination corridors should be established for ambulatory and non-ambulatory victims.

Consider appropriate management of chemically contaminated children, such as measures to reduce separation anxiety if a child is separated from a parent or other adult.

Decontamination Zone

Patients exposed only to hydrogen cyanide gas who have no eye irritation just need to remove outer clothing and wash their hair. Other patients will require decontamination as described below. Rapid decontamination is critical to prevent further absorption by the patient and to prevent exposure to others.

Decontamination Zone

Rescuer Protection

Personnel should continue to wear the same level of protection as required in the Hot Zone.

If exposure levels are determined to be safe, decontamination may be conducted by personnel wearing a lower level of protection than that worn in the Hot Zone. However, do not attempt resuscitation without a barrier.

ABC Reminders

Speed is critical. If the victim is symptomatic, immediately institute emergency life support measures including the use of a cyanide specific antidote (IOs can be placed utilizing a drill to enable acute administration of IV antidotes) as well as 100% oxygen. Treatment should be given simultaneously with decontamination procedures. Quickly ensure that the victim has a patent airway. Maintain adequate circulation. Stabilize the cervical spine with a decontaminable collar and a backboard if trauma is suspected. Assist ventilation with a bag-valve-mask device equipped with a canister or air filter, if necessary. Direct pressure should be applied to control heavy bleeding, if present.

Children and the elderly are at increased risk for hypothermia - provide warm showers, blankets.

Privacy must be considered, if possible.

The decontamination system should be designed for use in children of all ages, by parentless children, the non-ambulatory child, the child with special needs, and also allow families to stay together.

Use step-by-step child-friendly instructions that explain to the children and parents what they need to do, why they are doing it and what to expect.

Take into consideration that infants when wet are slippery and will need a way to get them through the decontamination process - i.e. plastic buckets, car seats, stretchers...

Designate a holding area and provide staff to support and supervise the children.

Recommended age appropriate staffing ratios for untended children:

1 adult to 4 infants

1 adult to 10 preschool children

1 adult to 20 school-age children

Washing Instructions

If there will be significant delay to decontamination have the victims rinse off with water exposed skin surfaces and disrobe (disposable clothing kits should be available).

Remove all clothing (at least down to their undergarments) and place the clothing in a labeled durable 6-mil polyethylene bag (removal of clothing, at least to the undergarment level will reduce victim's contamination by 85 %).

For liquid agent exposure If the clothes have been exposed to contamination, then extreme care must be taken when undressing to avoid transferring chemical agents to the skin - i.e. any clothing that has to be pulled over your head should be cut off instead of being pulled over your head .

Cover all open wounds with plastic wrap prior to performing head to toe decontamination (particular attention should be made to open wounds because cyanide is readily absorbed through abraded skin).

Flush the exposed skin and hair with plain water for 2 to 3 minutes then wash twice with mild soap. Rinse thoroughly with water. Be careful not to break the patient/victim's skin during the decontamination process.

Caution - many people shower as they do it at home rather than conducting a rapid decontamination of their bodies. Too aggressive scrubbing can lead to further damage to skin and open wounds.

Irrigate exposed or irritated eyes with plain water or saline for 5 minutes. Continue eye irrigation during other basic care or transport. Remove contact lenses if easily removable without additional trauma to the eye.

Utilizing large amounts of water by itself is very effective (limit pressure in infants).

If water supplies are limited, and showers are not available an alternative form of decontamination is to use absorbent powders such as flour, talcum powder, or Fuller's earth (0.5% sodium hypochlorite solution is contraindicated).

Sodium hypochlorite is not recommended for use in infants and young children.

Certification of decontamination is accomplished by any of the following: processing through the decontamination facility; M256A1 chemical agent detector kit (liquid and vapor), M18A2, M90 chemical agent detectors (vapor)

If still contaminated, repeat shower procedure.

Decontamination of First Responder:

Begin washing PPE of the first responder using soap and water solution and a soft brush. Always move in a downward motion (from head to toe). Make sure to get into all areas, especially folds in the clothing. Wash and rinse (using cold or warm water) until the contaminant is thoroughly removed.

Remove PPE by rolling downward (from head to toe) and avoid pulling PPE off over the head. Remove the SCBA after other PPE has been removed.

Place all PPE in labeled durable 6-mil polyethylene bags.

Decontamination of Infants and Children

Decontamination of Children (HHS/AHRQ) provides a step-by-step decontamination demonstration in real time, and trains clinicians about the nuances of treating infants and children, who require special attention during decontamination.

Support Zone

Be certain that victims have been decontaminated properly (see Decontamination Zone above). Victims who have been decontaminated or who have been exposed only to vapor generally pose no serious risks of secondary contamination to rescuers. In such cases, Support Zone personnel require no specialized protective gear.

Support Zone

Re-triage

Following decontamination the patient should be reassessed; noting changes in triage category (if any), the need for, or the modification of, supportive therapy as well as the initiation or continuation of cyanide specific antidotes (See ABC reminders/Advanced Treatment).

Advanced Treatment

Patients who are in shock or have seizures should be treated according to advanced life support (ALS) protocols. These patients, or those who have arrhythmias, may be seriously acidotic; consider giving, under medical supervision, 1 mEq/kg intravenous of sodium bicarbonate.

Transfer to Medical Facility

Only decontaminated patients, or patients not requiring decontamination, should be transported to a medical facility. "Body bags" are not recommended.

If a cyanide-containing solution has been ingested, prepare the ambulance in case the victim vomits toxic material. Have ready several towels and open plastic bags to quickly clean up and isolate vomitus.

Patients who have only brief inhalation exposure and mild or transient symptoms may be discharged from the scene after their names, addresses, and telephone numbers are recorded. They should be advised to seek medical care promptly if symptoms develop or recur (see Patient Information Sheet ).